This invention relates generally to apparatus for removing impurities from the plasma in a fusion reactor, and, more particularly to apparatus for removing the helium ash from a deuterium-tritium plasma.
The most likely fuel for a fusion reactor is deuterium and tritium, which produces alpha particles (helium nuclei) and neutrons. The neutrons produced escape through the walls of the plasma confinement device and are used in generating useful external heat. The alpha particles slow down and collect in the plasma as a helium impurity. Minute amounts of oxygen may also be present as an impurity. Since continuous operation of a fusion reactor requires continuous removal of the fusion by-products and other impurities, the helium ash must be continuously removed from the plasma.
A current method of helium removal involves the limiter, which serves to position the plasma away from the confinement device walls. Typically slots are provided in the limiter. Helium that drifts through the limiter slots is exhausted by a vacuum duct system behind the limiter. Another method involves a divertor, which is usually positioned below the plasma, away from the limiter. A magnetic field is used to divert the escaping alpha particles away from the plasma, where they form helium atoms, which are exhausted by a vacuum duct system. While the vacuum duct system is believed to provide adequate impurity control, it requires extensive structural components which must be fitted to the fusion reactor. Also, since some of the fuel ions would also be swept away in the vacuum system, the tritium must be recycled and a larger inventory of tritium must be available for the reactor.
Therefore, it is an object of the present invention to provide an apparatus for removing impurities from the plasma in a fusion reactor without an external vacuum pumping system.
It is also an object of the present invention to provide an apparatus for removing the helium ash from a fusion reactor.
It is another object of the present invention to provide an apparatus which removes helium ash and minimizes tritium recycling and inventory.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.